US4484819A - Reflectometer - Google Patents
Reflectometer Download PDFInfo
- Publication number
- US4484819A US4484819A US06/388,863 US38886382A US4484819A US 4484819 A US4484819 A US 4484819A US 38886382 A US38886382 A US 38886382A US 4484819 A US4484819 A US 4484819A
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- US
- United States
- Prior art keywords
- light
- tube
- sensor
- open end
- light sensor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/47—Scattering, i.e. diffuse reflection
- G01N21/4738—Diffuse reflection, e.g. also for testing fluids, fibrous materials
- G01N21/474—Details of optical heads therefor, e.g. using optical fibres
Definitions
- This invention is a light reflectometer.
- this invention is for a reflectometer that permits a direct measurement of absorptivity, ⁇ , of a surface.
- absorptivity has been guessed at or measured under laboratory conditions. There is no previous way of making a direct measurement of a surface in field conditions at any given time. No previously portable devices for measuring reflectivity and absorptivity are known.
- a reflectometer is mounted in a tube with a voltage source, light, diffuser, and light sensor.
- the light sensor is shielded from the diffuse light caused by direct illumination.
- the tube is also configured to serve as a light shield or a separate device forming a light shield is mounted at one end of the tube. The tube is placed against this surface causing a portion of the surface to be deprived of all external light. Only light incident on this surface from the diffused light source within the tube is available.
- Light reflected from the enclosed surface is monitored by the light sensor which is a cadmium sulfide photocell. As the amount of reflected light increases, the photocell provides a linear increase in resistivity. The resistance present is read out on any appropriate device such as a liquid crystal display.
- FIG. 1 is a cross-sectional view of the present invention.
- FIG. 2 is a circuit diagram of a circuit suitable for use in the present invention.
- Reflectivity is the ratio of reflected radiation to the incident radiation.
- Absorptivity, ⁇ is the ratio of the radiation which an object absorbs to the total radiation it receives.
- absorptivity can easily be determined if reflectivity is known.
- While reflectivity of a surface for visible light may be easily judged, the infrared and ultraviolet radiation characteristics may not be similar.
- a material may have high reflectivity for visible and ultraviolet light and low reflectivity for infrared radiation.
- a measure of reflectivity requires an instrument that can measure all wavelengths of incoming solar radiation needed for accurate calculations.
- FIG. 1 is a cross-sectional view of a reflectometer 10.
- Reflectometer 10 has an aluminum tube 12 which serves as a housing for the various components.
- a handle 14 is mounted to tube 12.
- a light 16 is mounted within a reflector 18 placed within tube 12.
- a diffuser 20 is placed in front of light 16. The diffused light is reflected from the surface to be measured and measured with a sensor 22 for reflected light intensity.
- Light sensor 22 can be any suitable photocell. Ideal choice would provide a sensor 22 which approximates the solar system characteristics. Such a sensor is a cadmium sulfide photocell. Cadmium sulfide photocell is also usually calibrated because it changes internal resistance with the change in the intensity of light incident on it.
- a seal 24, such as foam rubber, is used to block external light from reaching the surface being tested. Seal 24 can be glued or otherwise mounted to tube 12. The amount of light striking sensor 22 varies linearly with reflectivity of the material being measured. Thus, the electrical output from sensor 22 varies in direct proportion to the reflectivity of the material being measured.
- a circuit board 26 amplifies the electrical output of sensor 22, converts it to a digital or other signal and displays it on a readout device 28. Readout device 28 can be a meter or liquid crystal display.
- Tube 12 Sensor 22 and reflector 18 are held in fixed position within tube 12 by stopper 30 and spacer 32.
- the end of tube 12 is enclosed with a plastic housing 34 which contains a cover plate 36.
- FIG. 2 shows a detailed schematic for circuit board 26.
- Sensor 22 is represented by a dashed circle.
- a standard battery 40 such as a 12-volt battery, is sufficient for light 16.
- V out changes.
- the resistance of a cadmium sulfide sensor changes from 6,000 ohms to 16,000 ohms as the percent of reflected light varies from 0% to 100%.
- FIG. 2 is a voltage divider network.
- the cadmium sulfide sensor 22 is placed in voltage divider network 26. As the resistance of CDS sensor 22 changes, the different output voltage, V out , is produced from this network. To take advantage of this cadmium sulfide sensor change from 6,000 ohms to 16,000 ohms, it is desired to have a change in voltage of 1 volt over this resistance change. To determine the appropriate value for R 1 , the value of R 1 can be set at either 2.7K ohms or 35K ohms. For reasons of stability, 2.7K ohms is preferred. For a 12-volt battery as battery 40, the resistor functions with an output voltage range of approximately 4-5 volts.
- An internal analog-to-digital converter is used normally with acceptable voltages between -2 and 2 volts. Therefore, the output voltage from the voltage divider network needs to be shifted and inverted such that approximately 4 volts represents 100% reflectivity and 5 volts represents 0% reflectivity. This is done by using an inverting amplifier 42 with unity gain and supplying a reference voltage V ref to the positive input of amplifier 42.
- Amplifier 42 can be a commercial 741 op amp. It is found that the reference voltage V ref is approximately 2.5 volts with this arrangement.
- the reflectometer can be calibrated by placing it on a surface of high reflectivity, approximately 90%, and adjusting R 1 until the readout mechanism, such as a liquid crystal display, reads 90%. The instrument is then placed on a surface of known low reflectivity, approximately 10%, and R 2 is adjusted until the display reads 10%. Repetition of this procedure normally permits the reflectometer to slide into calibration.
- Cadmium sulfide photocell sensors have a maximum sensitivity wavelength of approximately 0.55 microns. Response is approximately linear and has a response curve similar to that for solar radiation. Internal light source 16 has to be considered such that the sensitivity matches the solar energy spectrum. A good match is obtained assuming the light to have a color temperature of 2850° K. The total instrument response is equal to the sensor response times the light source spectral transmissivity. For zero instrument error, the instrument response should match the solar energy spectrum. In general, the back of sensor 22 is shielded so that no diffused light can reach the front of sensor 22 which receives reflected light.
Abstract
Description
Claims (4)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US06/388,863 US4484819A (en) | 1982-06-16 | 1982-06-16 | Reflectometer |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US06/388,863 US4484819A (en) | 1982-06-16 | 1982-06-16 | Reflectometer |
Publications (1)
Publication Number | Publication Date |
---|---|
US4484819A true US4484819A (en) | 1984-11-27 |
Family
ID=23535845
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US06/388,863 Expired - Fee Related US4484819A (en) | 1982-06-16 | 1982-06-16 | Reflectometer |
Country Status (1)
Country | Link |
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US (1) | US4484819A (en) |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4801804A (en) * | 1986-09-30 | 1989-01-31 | Trebor Industries, Inc. | Method and apparatus for near infrared reflectance measurement of non-homogeneous materials |
US4880304A (en) * | 1987-04-01 | 1989-11-14 | Nippon Colin Co., Ltd. | Optical sensor for pulse oximeter |
FR2637980A1 (en) * | 1988-10-17 | 1990-04-20 | Bertin & Cie | IN SITU COLORIMETRIC INFORMATION COLLECTION DEVICE, ESPECIALLY ON AN ENOUGH TOOTH |
US4928014A (en) * | 1988-10-03 | 1990-05-22 | Futrex, Inc. | Near-infrared apparatus and method for determining percent fat in a body |
US5028787A (en) * | 1989-01-19 | 1991-07-02 | Futrex, Inc. | Non-invasive measurement of blood glucose |
WO1992000514A1 (en) * | 1990-06-29 | 1992-01-09 | Tma Technologies, Inc. | Modular scatterometer with interchangeable scanning heads |
US5157254A (en) * | 1991-02-19 | 1992-10-20 | Anderson John D | Reflective electro-luminescent measurement adapter for quality control of baked and fried goods |
US20120174910A1 (en) * | 2009-06-08 | 2012-07-12 | Ori Gil | Solar field and method for assembling the solar field |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3327583A (en) * | 1962-07-16 | 1967-06-27 | Lion Res Corp | Apparatus with diffusely reflecting hollow housing for measuring absolute reflectivity of a surface and the like |
US3421821A (en) * | 1964-12-10 | 1969-01-14 | Patrick A Alessi | Color spectrum analyzer |
FR2414726A1 (en) * | 1978-01-11 | 1979-08-10 | Agronomique Inst Nat Rech | Portable reflectometer incorporating plastics filter and pressure pad - used for determining the reflectance of meat and meat prods. and for determining their colour |
-
1982
- 1982-06-16 US US06/388,863 patent/US4484819A/en not_active Expired - Fee Related
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3327583A (en) * | 1962-07-16 | 1967-06-27 | Lion Res Corp | Apparatus with diffusely reflecting hollow housing for measuring absolute reflectivity of a surface and the like |
US3421821A (en) * | 1964-12-10 | 1969-01-14 | Patrick A Alessi | Color spectrum analyzer |
FR2414726A1 (en) * | 1978-01-11 | 1979-08-10 | Agronomique Inst Nat Rech | Portable reflectometer incorporating plastics filter and pressure pad - used for determining the reflectance of meat and meat prods. and for determining their colour |
Cited By (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4801804A (en) * | 1986-09-30 | 1989-01-31 | Trebor Industries, Inc. | Method and apparatus for near infrared reflectance measurement of non-homogeneous materials |
US4880304A (en) * | 1987-04-01 | 1989-11-14 | Nippon Colin Co., Ltd. | Optical sensor for pulse oximeter |
US4928014A (en) * | 1988-10-03 | 1990-05-22 | Futrex, Inc. | Near-infrared apparatus and method for determining percent fat in a body |
FR2637980A1 (en) * | 1988-10-17 | 1990-04-20 | Bertin & Cie | IN SITU COLORIMETRIC INFORMATION COLLECTION DEVICE, ESPECIALLY ON AN ENOUGH TOOTH |
WO1990004762A1 (en) * | 1988-10-17 | 1990-05-03 | Bertin & Cie | Apparatus for taking in situ colorimetric information, particularly on a tooth in a mouth |
EP0367647A1 (en) * | 1988-10-17 | 1990-05-09 | Bertin & Cie | Device for gathering colorimetric information in situ, especially at a tooth in the mouth |
US5028787A (en) * | 1989-01-19 | 1991-07-02 | Futrex, Inc. | Non-invasive measurement of blood glucose |
WO1992000514A1 (en) * | 1990-06-29 | 1992-01-09 | Tma Technologies, Inc. | Modular scatterometer with interchangeable scanning heads |
US5196906A (en) * | 1990-06-29 | 1993-03-23 | Tma Technologies, Inc. | Modular scatterometer with interchangeable scanning heads |
US5157254A (en) * | 1991-02-19 | 1992-10-20 | Anderson John D | Reflective electro-luminescent measurement adapter for quality control of baked and fried goods |
US20120174910A1 (en) * | 2009-06-08 | 2012-07-12 | Ori Gil | Solar field and method for assembling the solar field |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: UNITED STATES OF AMERICA AS REPRESENTED BY THE SEC Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:ULRICH, RICHARD D.;REEL/FRAME:004008/0754 Effective date: 19820607 Owner name: UNITED STATES OF AMERICA AS REPRESENTED BY THE SEC Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:ULRICH, RICHARD D.;REEL/FRAME:004008/0754 Effective date: 19820607 |
|
FPAY | Fee payment |
Year of fee payment: 4 |
|
REMI | Maintenance fee reminder mailed | ||
LAPS | Lapse for failure to pay maintenance fees | ||
FP | Expired due to failure to pay maintenance fee |
Effective date: 19921129 |
|
STCH | Information on status: patent discontinuation |
Free format text: PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362 |